Considerable progress has been made in recent years in the production of sintered metal articles from iron-base, nickel-base, copper-base, aluminum-base and beryllium-base metal powders such that sintered metal articles or parts are widely used in industry.
However, sintered articles or parts produced from the foregoing metal powders generally find limited use in areas calling for resistance to wear and abrasion, particularly sintered parts made of low carbon steel, certain nickelbase alloys and, of course, parts made of aluminum and copper.
One method which has been proposed for improving the wear resistance of sintered aluminum articles or parts is to incorporate into the aluminum powder mix an effective amount of particles of an alloy selected from the group consisting of nickel and cobalt in the form of a hard intermetallic compound which is dispersed throughout the aluminum matrix in the finely sintered state. The foregoing concept is disclosed in U.S. Pat. No. 4,015,947 (Apr. 25, 1977).
It would be desirable to employ particles of refractory metal carbides as a hard phase but such carbides, particularly titanium carbide, do not bond easily during solid state sintering with such metal powders as aluminum-base and copper-base powders, as well as nickel-base and iron-base powders.
It is known to produce a reinforced heat resistant metal product in which 5% to 20% by volume of a finely divided slip and recovery-inhibiting phase, e.g. carbides, borides, etc., of refractory metals, is mixed with a heat resistant metal, such as an 80-20 nickel-chromium alloy powder and formed into a sintered shape which is thereafter substantially hot worked to a reduction of at least 50% of its original cross sectional area. In this manner, a certain amount of bonding is obtained between the hard phase and the metal matrix by vigorous hot working. Such a process is disclosed in U.S. Pat. No. 2,852,367 (Sept. 16, 1959).
It is important that bonding be achieved between the hard phase and the metal matrix, particularly a non-ferrous metal matrix, so that the hard phase will remain anchored in the matrix in applications involving wear such as occurs in sliding friction; otherwise, the hard phase not adequately bonded tends to be dislodged, thus giving rise to progressive wear of the sintered part which can be accelerated under conditions involving fretting corrosion.
It would thus be desirable to provide a method for producing a sintered shape from iron-base, nickel-base, aluminum-base and copper-base powder in which refractory metal carbides are employed as an additive to confer improved resistance to wear and abrasion to said shape.